Powder spray lubricant of molybdenum disulfide

ABSTRACT

A powder spray lubricant of molybdenum disulfide including 1 to 10% (by mass) of molybdenum disulfide powder having a particle diameter in the range of 0.1 to 200 μm and 90 to 99% (by mass) of a high-pressure gas pressurized at 0.3 MPa or more in combination is disclosed. A powder spray lubricant of molybdenum disulfide including 1 to 10% (by mass) of molybdenum disulfide powder having a particle diameter in the range of 0.1 to 200 μm, 1 to 10% (by mass) of oil, 1 to 10% (by mass) of an organic solvent and 70 to 97% (by mass) of a high-pressure gas pressurized at 0.3 MPa or more in combination is disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lubricant that is used, in automobiles and various kinds of industrial machines such as construction machines, with an intention of being worn, in a sliding surface that is required to be load resistant, low in the wear properties and low in the friction properties.

2. Description of the Related Art

In comparison with all-purpose grease and oil, lubricants including a solid lubricant are high in the lubrication effect and used in a special field of lubrication. Here, as the solid lubricant, for instance, molybdenum disulfide, graphite, PTFE or the like is used.

The lubricant including a solid lubricant is mixed with a liquid material such as grease, paste or oil and used. As an example thereof, an invention of a rust preventive lubricant in which molybdenum disulfide (hereinafter referred to as MoS₂) is mixed with rust preventive oil is proposed.

Furthermore, as another example, an invention of a high temperature use lubricant composition in which in a dispersing medium containing trialkyl phosphate MoS₂ powder is dispersed and a surfactant is mixed is proposed.

In so far known grease, paste or oil containing a solid lubricant, there is a problem in that, although the lubrication effect can be improved more than the grease or the like, in comparison with the solid lubricant, under high load the lubrication effect is deteriorated.

This can be easily understood when applications are considered. That is, this is because the grease or the like containing a solid lubricant is used in a place where the solid lubricant is difficult to use, for instance, in a place where a coating method of the solid lubricant cannot be found.

This is because, when a solid lubricant is difficult to apply on a sliding surface, by relying on the adhesiveness of the grease, paste or oil that is adhesive and easy to coat, the grease or the like containing a solid lubricant has to be used.

However, there is a problem in that when the solid lubricant is attached to a sliding surface, as a result of using the adhesiveness of the grease or the like, regarding demands for the load resistance, the low wear properties and the low friction properties, the characteristics of the solid lubricant have to be sacrificed.

SUMMARY OF THE INVENTION

In the present invention, only powder of solid lubricant (MoS₂) is used. That is, the grease or the like is not used. The powder of solid lubricant (MoS₂) is sprayed to a sliding surface under high pressure and thereby a lubrication layer of the solid lubricant (MoS₂) is successfully disposed on the sliding surface. Thus, the MoS₂ powder is enabled to easily attach to a sliding surface, and thereby the foregoing existing problems are overcome.

That is, in a powder spray lubricant of molybdenum disulfide, which is proposed by the invention, 1 to 10% (by mass=by weight) of molybdenum disulfide powder and 90 to 99% (by mass=by weight) of a high-pressure gas are combined.

Furthermore, in another powder spray lubricant of molybdenum disulfide, which is also proposed by the invention, 1 to 10% (by mass=by weight) of molybdenum disulfide powder, 1 to 10% (by mass=by weight) of oil, 1 to 10% (by mass=by weight) of an organic solvent, and 70 to 97% (by mass=by weight) of a high-pressure gas are combined.

The latter powder spray lubricant according to the invention, in comparison with the former powder spray lubricant in which only molybdenum disulfide powder and a high-pressure gas are combined, does not cause the deficiency in the adhesiveness under whatever conditions and applications. That is, in comparison with the former powder spray lubricant of the present invention, an expected purpose that the solid lubricant exhibits can be advantageously achieved by the latter powder spray lubricant of the present invention.

That is, according to the powder spray lubricant of the present invention, which is made of a combination of the molybdenum disulfide powder, oil, organic solvent and high-pressure gas, by adding a slight amount of oil as a medium, a surface of which antifriction is intended can be wetted by this oil and thereby a liquid lubrication film can be formed on the surface of which antifriction is intended. Furthermore, by using a slight amount of solvent to dilute and thereby to render sprayable, without damaging the characteristics as almost pure powder spray, the powder spray lubricant can be made sprayable.

Furthermore, not only the organic solvent but also the oil added slightly as a medium can be very readily volatilized at a temperature of 200° C. or more. Accordingly, when the powder spray lubricant of the present invention is sprayed under pressure on a surface of which antifriction is intended (antifriction target surface), the organic solvent and oil are volatilized and only MoS₂ powder is left. So that, higher lubrication effect of the solid lubricant can be exhibited.

In place of the oil in the above, as a medium, grease, a paint binder or the like can be used. However, when the powder spray lubricant of molybdenum disulfide according to the invention is applied to a cylinder, oil can be preferably used as the medium.

As the oil, an oil which can be vaporized as completely as possible without leaving a residual component (carbon) by heating may be used. For example, a synthetic ester base oil or polyether base oil can be desirably used as the before described oil.

Furthermore, as the organic solvent, a hydrocarbon base solvent, a ketone base solvent or an aromatic solvent can be used. However, from a viewpoint of the environment problem the hydrocarbon base solvent is preferably used.

When contents of the oil and organic solvent each are set at 1% or less (by mass) in the powder spray lubricant, the adhesiveness becomes deficient and the adhesion state becomes unfavorably irregular. On the other hand, when contents of the oil and organic solvent each are set at 10% or more (by mass) in the powder spray lubricant, there is no further improvement in the effect; accordingly, the upper limit is set at 10%. A preferable content of each of the oil and organic solvent is in the range of 2 to 8% (by mass).

In all of powder spray lubricants of molybdenum disulfide according to the invention, a particle diameter of molybdenum disulfide powder is preferably in the range of 0.1 to 200 μm.

When the particle diameter of MoS₂ powder is set at 0.1 μm or less, since there is no change in the effect, the lower limit thereof is set at 0.1 μm. Furthermore, when the particle diameter thereof is set at 200 μm or more, since there is a fear that a sliding surface on which MoS₂ is sprayed may become irregular, the upper limit is set at 200 μm.

In all of powder spray lubricants of molybdenum disulfide according to the invention, when a concentration of MoS₂ becomes 1% or less (by mass), there is a fear of the deterioration in the antifriction layer formation efficiency. On the other hand, when the concentration becomes 10% or more (by mass), from the relationship with a high-pressure gas, the uniformity may be unfavorably damaged.

Although it is not easy to flatly determine the concentration of MoS₂ since the relationship between the concentration of MoS₂ and the particle diameter of MoS₂ must be considered, when an average particle diameter is 10 μm, the concentration of MoS₂ is preferably in the range of 4 to 7% (by mass).

In any of powder spray lubricants of molybdenum disulfide according to the invention, the high-pressure gas is used to spray the powder spray lubricant of the present invention. As the high-pressure gas, for instance, LPG can be used. In order that the powder spray lubricant of the present invention may be sprayed on a surface of which antifriction is intended (antifriction target surface) and may be assuredly attached thereto, the pressure is preferably set at 0.3 MPa or more. Normally, a high-pressure gas in the range of 0.3 to 0.5 MPa is used.

In a method of use of a powder spray lubricant of molybdenum disulfide of the present invention, the powder spray lubricant of molybdenum disulfide of the present invention is sprayed under pressure on a surface of which antifriction is intended (antifriction target surface). For instance, the powder spray lubricant of molybdenum disulfide of the present invention is accommodated in a pressure-resistant vessel having a spray nozzle and sprayed under pressure on an antifriction target surface from the spray nozzle. At this time, the pressurizing force is preferably 0.3 MPa or more.

The pressurizing force intends to spray MoS₂ on a sliding surface (antifriction target surface) and to assuredly attach thereto and, in the range of 0.3 MPa or more, normally, the pressurizing force in the range of 0.3 to 0.5 MPa is used.

For instance, by use of LPG pressurized at 0.3 MPa or more as a spraying high-pressure gas, when 95% (by weight=by mass) of the high-pressure gas and 5% (by weight=by mass) of MoS₂ powder (average particle diameter: 10 μm) are mixed, a powder spray lubricant of molybdenum disulfide according to the invention can be obtained. When this is sprayed on a sliding surface (antifriction target surface) under pressure of 0.3 MPa or more, 9 m² thereof can be sprayed every minute.

When a sliding surface (antifriction target surface) is cylindrical in the above (for instance, an inner surface of a cylinder), at a tip end of a spray nozzle of a vessel in which the powder spray lubricant according to the invention is filled, many spray holes are arranged along a circumferential direction, and thereby the lubricant can be uniformly sprayed on the inner surface of the cylinder. Furthermore, when a relatively narrow gap wall surface is a sliding surface (antifriction target surface), when many spraying holes are disposed on a sidewall of a slender nozzle and the nozzle is reciprocated back and forth and around, an object can be easily achieved.

The powder spray lubricant of molybdenum disulfide according to the invention can be readily attached to a surface of which antifriction is intended (antifriction target surface). Accordingly, in comparison with existing lubricants containing a solid lubricant, in which a solid lubricant is mixed with grease, paste or oil, the lubrication effect under high load can be very much improved. Furthermore, by spraying by use of a high-pressure gas, the powder spray lubricant according to the invention can be attached to the antifriction target surface; accordingly, the powder spray lubricant can be readily attached to a sliding surface that is so far difficult to coat, and thereby the antifriction property on such a sliding surface (antifriction target surface) can be exhibited.

Furthermore, when MoS₂ powder is attached to the sliding surface (antifriction target surface), there is no need of using the grease or the like. Accordingly, even when oil is used as a medium, the oil can be completely vaporized by heating, and thus excellent load resistant properties, low wear properties and low friction properties can be exhibited.

Still furthermore, according to the invention, the handling of the lubricant becomes convenient, a method of use thereof is also simple and easy; accordingly, there is no need of special skill.

EXAMPLE 1

In a pressure-resistant vessel having a spray nozzle, 5% (by mass=by weight) of MoS₂ having an average particle diameter of 10 μm and 95% (by mass=by weight) of LPG at 0.3 MPa as a high-pressure gas are accommodated.

In the above, when a valve pertained to a nozzle is opened, MoS₂ is discharged from the nozzle together with a high-pressure gas. When the nozzle is disposed opposite to a sliding surface surface (antifriction target surface) with a gap of for instance 10 cm, as the high-pressure gas is discharged, MoS₂ is discharged, and thereby a layer of MoS₂ is formed on the sliding surface surface (antifriction target surface).

Here, MoS₂ powder having an average particle diameter of 10 μm is used; however, a mixture of powders having a particle diameter in the range of 0.1 to 200 μm can be used without disadvantage from a viewpoint of effect.

In the example, LPG is used; however, all liquefied gases normally used in the spraying can be used.

EXAMPLE 2

In a pressure-resistant vessel having a spray nozzle, a powder spray lubricant of molybdenum disulfide according to the invention, which contains 5% (by mass=by weight) of MoS₂, 5% (by mass=by weight) of oil, 6% (by mass=by weight) of an organic solvent and 84% (by mass=by weight) of LPG pressurized at 0.4 MPa was filled. MoS₂ had an average particle diameter of 10 μm, as an oil content of the medium ester base oil was used and as the organic solvent a hydrocarbon base solvent was used.

In the above, when a valve pertained to a nozzle is opened MoS₂ is discharged from the nozzle together with a high-pressure gas.

The powder spray lubricant according to the invention was sprayed from a plug hole of an automobile engine into a cylinder and coated. To a cylinder volume of 500 cc, 15 to 20 cc of the powder spray lubricant was used. Thereafter, by leaving for 20 hr, the powder spray lubricant was dried.

The organic solvent excluding solid powder (MoS₂ powder) containing liquid oil is instantaneously dried owing to a high-pressure gas immediately after the spraying; accordingly, the powder (MoS₂ powder) is attached to a sliding surface.

In a sliding state when an engine is used, powders that are fine particles slightly containing oil content are compressed and coated on fine irregular surfaces of materials sliding each other, and thereby a coated state excellent in the planar properties can be obtained.

In the example, MoS₂ powder having an average particle diameter of 10 μm was used; however, a mixture of powders having a particle diameter in the range of 0.1 to 200 μm can be used without disadvantage from a viewpoint of effect.

In the example, LPG was used; however, all liquefied gases normally used in the spraying can be used.

In the above, after leaving for 20 hr, a dry adhesion state was confirmed. Thereafter, an engine performance test was carried out with an engine dynamometer. Thereby, as described below, it was confirmed that the pressure, torque and compression were improved over substantially whole regions and that the sound level and an amount of exhaust gases CO and HC were lowered.

According to the experimental results, advantageous effects such as shown below were confirmed.

1. Horsepower: in the range of 3000 to 7000 rpm, a maximum increase of 4.6 PS was confirmed (over substantially whole region).

2. Torque: in the range of 3000 to 7000 rpm, a maximum increase of 0.51 kg·m was confirmed (over substantially whole region).

3. Sound level: in the range of idling engine speed of 3000 to 5000 rpm, a maximum decrease of 1.7 dB was confirmed (over substantially whole region).

4. Compression: in the range of 3000 to 7000 rpm, an increase of 0.1 to 0.2% was confirmed (over substantially whole region).

5. CO: a decrease from normal 3 to 6% by volume to 2 to 5% by volume (a decrease of 19% in average).

HC: a decrease from normal 410 to 610 ppm to 330 to 500 ppm (a decrease of 19% in average).

Although only preferred embodiments and examples have been described specifically so far, it may be appreciated that many modifications and variations of the present invention are possible in light of the above teachings and without departing from the spirit and intended scope of the invention. 

1. A powder spray lubricant of molybdenum disulfide, comprising 1 to 10% (by mass) of molybdenum disulfide powder and 90 to 99% (by mass) of a high-pressure gas in combination.
 2. A powder spray lubricant of molybdenum disulfide, comprising 1 to 10% (by mass) of molybdenum disulfide powder, 1 to 10% (by mass) of oil, 1 to 10% (by mass) of an organic solvent and 70 to 97% (by mass) of a high-pressure gas in combination.
 3. The powder spray lubricant of molybdenum disulfide according to claim 1, wherein a particle diameter of the molybdenum disulfide powder is in the range of 0.1 to 200 μm.
 4. The powder spray lubricant of molybdenum disulfide according to claim 2, wherein a particle diameter of the molybdenum disulfide powder is in the range of 0.1 to 200 μm. 